Acknowledgements

These data were collected and made freely available by the Coriolis project and programmes that contribute to it (http://www.coriolis.eu.org ).

These data were collected and made freely available by the International Argo Project and the national programmes that contribute to it (http://www.argo.ucsd.edu, http://argo.jcommops.org).

Argo is a pilot programme of the Global Ocean Observing System.